The small and large intestinal site and mechanism of absorption of the fat soluble vitamins will be investigated. Major emphasis will be placed on the absorption of vitamin K which will be used as a model system for the investigation of the other fat soluble vitamins. Using a modified everted gut sac technique and perfused intestinal segments in-vitro the absorption mechanisms and site of vitamin A-1 and the hydroxylated metabolites of vitamin D-3 will be investigated. The effects of the presence or absence of bile salts, fatty acids, and the other fat soluble vitamins on the absorption of the above compounds will be investigated. The absorption of the fat soluble vitamins will be investigated in-vivo in the rat assessing the absorption mechanisms, the apparent Km and Vmax of the above compounds in the various regions of the small bowel. The effect of the presence or absence of biliary secretions, pancreatic secretions, and fatty acids in the intestinal contents, the effect of modification of the chain length and degree of saturation of fatty acids, and the effect of metabolic inhibitors and uncouplers will all be investigated with respect to the absorption of the fat soluble vitamins in-vivo. The absorption mechanisms and site of absorption of the fat soluble vitamins in normal human volunteers will be investigated by small intestinal intubation techniques. Data from human experimentation will be compared and contrasted to information gained from previous animal experimentation both in-vitro and in-vivo. Oral absorption of the fat soluble vitamins when administered together with a standard test meal will be assessed in normal human volunteers and in patients with diseases of the bowel, the liver, or the pancreas which may adversely affect the absorption of lipids.